2. For moderate aplastic anemia, fulfills any two of the following three criteria: absolute neutrophil count less than 1200/ul; hemoglobin less than 8 g/dL with corrected reticulocyte count less than 1%; and platelet count less than 60,000/uL (Note: Participants who have progressed from moderate to severe aplastic anemia prior to study entry will be classified as having severe aplastic anemia)